Another study points to climate harm from gas drilling

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Another study has found that global warming pollution from natural gas drilling and production is likely far greater than estimated by current government emissions inventories.

During two days of intensive airborne measurements, oil and gas operations in Colorado’s Front Range leaked nearly three times as much heat-trapping methane as predicted by current inventory estimates, according to the new study from the University of Colorado-Boulder.

The measurements also found that benzene emissions were seven times higher than existing inventories, and that emissions of other chemicals that contribute to smog were twice as high as estimates.

“These discrepancies are substantial,” said lead author Gabrielle Petron, an atmospheric scientist with the university’s National Oceanic and Atmospheric Administration Cooperative Institute for Research in Environmental Sciences.

“Emission estimates or ‘inventories’ are the primary tool that policymakers and regulators use to evaluate air quality and climate impacts of various sources, including oil and gas sources,” Petron said. “If they’re off, it’s important to know.”

The new study, published last week in the American Geophysical Union’s Journal of Geophysical Research: Atmosphere, provides confirmation of findings from research performed from 2008 to 2010 by Petron and her colleagues on the magnitude of air pollutant emissions from oil and gas activities in northeastern Colorado.

For years, the conventional wisdom was that natural gas was a good alternative to coal, producing half the carbon dioxide emissions per unit of energy when burned in a power plant. However, natural gas itself is mostly methane, a powerful greenhouse gas, and the conventional thinking didn’t take into account methane emissions during the process of drilling for, producing and transporting natural gas.

Three years ago, the issue gained much more attention with the publication of a study by a team of Cornell University researchers, led by ecology professor Robert Howarth. That study reported that natural gas could be just as bad — or worse — than coal for global warming, especially if the issue is examined on the short time frame in which scientists believe action is needed to curb global warming.

Since then, industry officials have harshly criticized Howarth’s study, and there’s been a lively debate in scientific journals about his results and about the many variables used to estimate methane emissions from the shale-gas boom across the country.

The natural gas boom in West Virginia and across the nation has brought climate-change benefits. Fuel-switching by utilities from coal to natural gas has — along with dramatic increases in renewable power generation — has helped reduce carbon dioxide emissions from the U.S. electricity sector to their lowest levels since 1994.

West Virginia political leaders tout natural gas as the state’s energy and economic future. They say the jobs will keep coming, and that spin-off businesses from natural gas production will eventually revitalize the state’s chemical-making industry.

President Obama is targeting greenhouse emissions from coal-fired power plants as part of his plan to combat climate change. But the administration has warmly embraced the natural gas boom, citing the switch from coal to gas for electricity generation as one way to combat climate change.

The new Colorado study is the latest to find that current emissions inventories for the oil and gas industry’s methane emissions likely underestimate those emissions.

“Accurate estimates of emissions from oil and natural gas operations at the regional and national level are still needed to quantify (and minimize) their impacts on climate forcing and air quality,” the study said.

Last month, a paper in the Proceedings of the National Academy of Sciences likewise reported methane emissions greater than existing estimates based on examination of natural gas wells in Pennsylvania.

“These regional scale findings and a recent national study indicate that overall site leak rates can be higher than current inventory estimates,” that paper said. “Additionally, a recent comprehensive study of measured natural gas emission rates versus ‘official’ inventory estimates found that the inventories consistently underestimated measured emissions and hypothesized that one explanation for this discrepancy could be a small number of high-emitting wells or components.

“These high leak rates illustrate the urgent need to identify and mitigate these leaks as shale gas production continues to increase nationally.”